Upon entry into the colonic environment, the 7α-hydroxyl group on cholic
acid is removed to produce deoxycholic acid by select members of the colonic
microbiota, including C. scindens (Ridlon et al., 2006). Deoxycholic acid inhibits
C. difficile vegetative growth (Sorg and Sonenshein, 2008). During antibiotic
treatment, the organisms that 7α-dehydroxylate bile acids are killed,
leading to an increased abundance of cholic acid derivatives in the colonic
environment (Theriot et al., 2014). These
compounds, in combination with glycine (Sorg and
Sonenshein, 2008), germinate C. difficile spores,
which can then grow out as vegetative cells and cause disease.